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Stress leads to premature birth and increases the birth rate of girls
Last reviewed: 16.10.2021
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According to a study published in the journal Human Reproduction, mothers who are stressed during the second and third trimester of pregnancy have an increased risk of premature birth. In addition, stress can affect the sex of the child, leading to a decrease in the birth rate of male infants.
The study examined the impact of stress caused by the earthquake in Chile in 2005 on pregnant women.
The fact that stress can shorten the period of pregnancy, scientists have known before, but a study that examines the impact of stress on the ratio of born boys and girls was conducted for the first time.
In Chile between 2004-2006, more than 200,000 births were recorded per year. The birth certificates of all babies born during this period were investigated by the scientists Florence Torche and Karine Kleinhaus from New York University (USA).
Each registration certificate of birth contained data on the gestational age at birth, weight, height and the field of the child. In addition, data were collected on the age of mothers during childbirth, previous pregnancies, marital status.
"Looking at the information about the gestational age in a large group of women at the time of the earthquake, we were able to determine how stress affects a woman in different gestational periods, depending on how close they were from the epicenter of the earthquake," said the author of the study Florencia Torche.
A team of scientists found that women who lived closest to the epicenter of the earthquake during the second and third trimesters of pregnancy had a high risk of premature birth.
Approximately 6 out of 100 women had premature births. In women exposed to an earthquake in the third trimester of pregnancy, the risk of developing preterm labor was higher by 3.4%.
The effect of stress on the course of pregnancy was most pronounced at the birth of girls, the likelihood of early delivery increased by 3.8% if the mother was in the third trimester and 3.9% if she was in the second trimester. In the premature birth of boys, no statistically similar effect was observed.
When analyzing the impact of stress on the ratio of born boys and girls, scientists found that the stress of the earthquake more significantly affected the early delivery of girls.
As a rule, the ratio of the birth of boys to girls is approximately 51:49. In other words, out of every 100 genera, in 51 cases, boys will be born. The data of scientists showed a 5.8% decline in this proportion, which is expressed in relation to 45 newborn boys per 100 children born.
The findings of scientists on the reduction in the sex ratio at birth confirm the hypothesis that stress can affect the viability of boys in the prenatal period of development.
[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]